A specific antibody, 6313/G2, to the N-terminus of the angiotensin II type I (AT1) receptor causes retention of the AT1 receptor in the plasma membrane of rat adrenal zona glomerulosa cells and stimulates steroidogenesis and inositol trisphosphate (IP3) release. Its effects are not significantly additive with those of angiotensin. In contrast, 6313/G2 completely inhibits angiotensin induced translocation of protein kinase C to the membrane fraction, although alone it has no effect. The data suggest that IP3 linked events, such as steroidogenesis, do not require receptor internalization, but protein kinase C activation does. They also confirm that protein kinase C activation is not required for stimulation of steroidogenesis in rat dispersed glomerulosa cells.